Indicators of periodontal disease were common in a large cohort of patients with established coronary heart disease and were associated with elevated cardiovascular risk, although causal links remain elusive, researchers found.

Patients with chronic coronary heart disease who participated in the STABILITY trial and had greater tooth loss tended to have greater burdens of various cardiovascular risk factors, according to Ola Vedin, MD, of Uppsala University in Sweden, and colleagues.

Gum bleeding also was associated with elevations in some cardiovascular risk factors, although the findings were less consistent than those seen with tooth loss, the researchers reported online in the European Journal of Preventive Cardiology.

"Not only do these observations suggest common risk factors for dental disease and coronary heart disease but [they] also raise the question whether self-reported dental health can be useful in assessing future cardiovascular risk in patients with coronary heart disease," they wrote.

"Although these descriptive analyses cannot confirm a causal relationship between dental health and cardiovascular risk, causality is widely accepted for certain associations, particularly smoking," they added. "For certain other relationships, including diabetes and obesity, causality and causal direction are debated and sometimes even a bidirectional association has been proposed."

Thus, the potential causal connection -- including the possibility that treating periodontal disease can reduce cardiovascular events -- needs to be studied further, they wrote.

Periodontal disease shares some risk factors with coronary heart disease, such as older age and smoking. But, although previous studies have identified relationships between gum disease and cardiovascular risk, the causal connection is tenuous. In 2012, the American Heart Association issued a scientific statement calling the relationship into question.

Vedin and colleagues explored the issue in a substudy of the STABILITY trial, which was conducted in 39 countries and included 15,828 patients with chronic coronary heart disease and at least one additional risk factor. The main results of the trial showed that the novel drug darapladib -- a selective oral inhibitor of lipoprotein-associated phospholipase A2 (Lp-PLA2) -- failed to reduce cardiovascular events.

According to a questionnaire completed at baseline, 40.9% of the patients had fewer than 15 teeth remaining, including 16.4% who had no teeth. In addition, 25.6% reported their gums bleeding at least sometimes. Rates of both indicators of periodontal disease varied widely according to country, regions within countries, and ethnic groups.

"The regional variation in periodontal disease prevalence can partly be explained by regional differences in cardiovascular risk factor prevalence; for instance, smoking," the authors wrote. "However, the considerable differences also seen among countries within the same region and between ethnic groups indicate a complex relationship in which demographic, genetic, and socioeconomic disparities are likely contributing factors."

The patients who retained more of their teeth had significantly lower fasting glucose levels, LDL cholesterol, systolic blood pressure, waist circumference, white blood cell count, and high-sensitivity C-reactive protein, and better kidney function (P≤0.001 for all). They also were less likely to have diabetes or to smoke and more likely to have a higher eduction level, to drink more alcohol, and to have more work stress.

Patients with at least some gum bleeding had significantly higher LDL cholesterol and systolic blood pressure. They were less likely to smoke, but were more likely to have a higher education level, to drink more alcohol, and to have higher levels of work, home, or financial stress.

Some of the inconsistencies in the relationships between indicators of periodontal health and cardiovascular risk -- greater alcohol consumption and more work stress in those with more teeth, for example -- were likely related to socioeconomic factors, according to the authors.

The reduced number of associations seen with gum bleeding compared with tooth loss "possibly [reflects] the fact that tooth loss, as opposed to gum bleeding, is a result of long-term chronic exposure to etiological factors that are at least partly common to both coronary heart disease and periodontal disease and could therefore result in stronger associations to cardiovascular risk," Vedin and colleagues wrote.

"Moreover, and unlike gum bleeding," they continued, "tooth loss can also have other causes than periodontal disease, including caries, trauma, and deliberate extractions, and may therefore not be treated strictly as an indicator of periodontal disease, but rather a marker of overall dental health and possibly even a marker of general health, socioeconomic factors, and psychosocial status, which could also contribute to its stronger association with cardiovascular risk."

The researchers acknowledged some limitations of the study, including the lack of an established measure to reflect manifest periodontal disease, potential residual confounding, possible recall bias regarding gum bleeding, and the lack of adjustment for the use of dual antiplatelet therapy and anticoagulation, which could have influenced the gum bleeding results.